1. Field of the Invention
This invention relates to a reclining seat which comprises a seat cushion, a seat back pivotally mounted to the seat cushion, first and second locking means provided at both sides of the seat for securing the seat back relative to the seat cushion, and a supporting shaft interconnecting the first locking means and the second locking means.
2. Description of the Related Art
Each of French Patent No. 2,578,602, Japanese Patent Application Laid-Open No. 8-253063 and U.S. Pat. No. 6,312,053 discloses locking means for securing a seat back relative to a seat cushion. The conventional locking means for securing a seat back relative to a seat cushion comprises a disk-shaped housing, a disk-shaped cover plate, the disk-shaped cover plate having an annular wall and teeth around an inner periphery of the annular wall, the cover plate being rotatably received in the housing in a face to face relation, a plurality of locking gears radially arranged within an inner surface of the housing between the housing and the cover plate, the locking gears each having a toothed surface and being movable between a locked position and an unlocked position, the toothed surfaces of the locking gears being adapted to engage the teeth of the cover plate in the locked position to secure the seat back relative to the seat cushion, a cam for engagement with the locking gears and selectively moving the locking gears between the locked position and the unlocked position, the cam being arranged within the inner surface of the housing between the housing and cover plate and surrounded by the locking gears, a shaft to which the cam is mounted for rotation with the shaft, the shaft extending through the housing and the cover plate, and an operating lever mounted to the shaft for actuating the cam. In the conventional locking means, when a user operates the operating lever, the shaft and the cam are rotated, whereby the locking gears are disengaged from the teeth of the cover plate. In this condition, the seat back is allowed to be reclined relative to the seat cushion.
In a case where the locking means is arranged at only one of both sides of a seat, there is a possibility that the seat back will be unable to be stably secured to the seat cushion. Therefore, if necessary, the locking means is arranged at each of the both sides of the seat. In this case, the operating lever is mounted to only the shaft of one of the first and second locking means. In order that the operating lever can provide rotation to the shaft of the other of the first and second locking means and the cam of the other of the first and second locking means, the shaft of the first locking means and the shaft of the second locking means are coupled to each other through a supporting shaft which is rigidly or fixedly connected at one end portion thereof to the shaft of the first locking means and is rigidly or fixedly connected at the other end portion thereof to the shaft of the second locking means. When the operating lever is operated, the shaft to which the operating lever is mounted is rotated, whereby the corresponding cam is rotated so as to cause the corresponding locking gears to be released from the teeth of the corresponding cover plate. Simultaneously, the rotation of the shaft to which the operating lever is mounted is transmitted to the shaft of the other of the first and second locking means, whereby the corresponding cam is rotated so as to cause the corresponding locking gears to be released from the teeth of the corresponding cover plate. In this condition, the seat back is allowed to be reclined relative to the seat cushion.
In state where the locking gears of the first locking means are released from the teeth of the cover plate of the first locking means, and the locking gears of the second locking means are released from the teeth of the cover plate of the second locking means, when the seat back is rotated relative to the seat cushion in order that the seat back is reclined at a desired angle to the seat cushion and secured relative to the seat cushion in the reclined state, torsion force is applied to the supporting shaft, since both end portions of the supporting shaft are rigidly or fixedly to the shafts of the first and second locking means. Therefore, when the operating lever is released from the user, there is a possibility that the locking gears of one of the first and second locking means can be normally meshed with the teeth of the corresponding cover plate whereas the locking gears of the other of the first second locking means may not be normally meshed with the teeth of the corresponding cover plate. Therefore, reclining angle of the seat back relative to the seat cushion will be unable to be smoothly adjusted and the seat back will be unable to be stably secured relative to the seat cushion.